Re: [ARM] PR66791: Replace calls to builtin in vmul_n (a, b) intrinsics with __a * __b

[Prathamesh Kulkarni via Gcc-patches]

On Mon, 31 May 2021 at 15:22, Prathamesh Kulkarni
<prathamesh.kulka...@linaro.org> wrote:
>
> On Wed, 26 May 2021 at 14:07, Marc Glisse <marc.gli...@inria.fr> wrote:
> >
> > On Wed, 26 May 2021, Prathamesh Kulkarni via Gcc-patches wrote:
> >
> > > The attached patch removes calls to builtins in vmul_n* (a, b) with __a * 
> > > __b.
> >
> > I am not familiar with neon, but are __a and __b unsigned here? Otherwise,
> > is vmul_n already undefined in case of overflow?
> Hi Marc,
> Sorry for late reply, for vmul_n_s*, I think they are signed
> (int<width>x<width>_t).
Oops, I meant int<width>x<nelems>_t.
> I am not sure how should the intrinsic behave in case of signed overflow,
> but I am assuming it's OK since vmul_s* intrinsics leave it undefined too.
> Kyrill, is it OK to leave vmul_s* and vmul_n_s* undefined in case of overflow 
> ?
>
> Thanks,
> Prathamesh
> >
> > --
> > Marc Glisse